The genus Haemophilus includes bacteria classified as such, for example, in Bergey's Manual of Systematic Bacteriology (P. H. A. Sneath, ed., 1984, pp. 558-569, Williams & Wilkins). Haemophilus bacteria are minute to medium sized gram-negative coccobacilli or rods generally less than 1 .mu.m in width and variable in length forming threads or filaments and showing marked polymorphism. They occur as obligate parasites on mucous membranes of man and a variety of animals. Capsules are present in a number of species and are of particular interest in Haemophilus influenzae, where they play a part in pathogenesis. The majority of Haemophilus influenzae strains can be assigned to any of six biovars (I-VI) on the basis of a few biochemical characteristics, and six serovars (A-F) have been identified on the basis of capsular polysaccharides. In addition, the species Haemophilus aegyptius has been shown to be the same species as Haemophilus influenzae (Casin et al., Ann. Microbiol. (Paris) 137B:155-163, 1986), and is now considered as another biovar of H. influenzae (Bergey's Manual of Determinative Biology, Hoft et al., eds., p. 195, Williams & Wilkins).
Haemophilus influenzae type b is a major cause of invasive diseases such as meningitis, epiglottiditis, arthritis, and cellulitis which occur exclusively in infants and children. In the United States, the annual incidence of invasive Haemophilus influenzae type b related diseases ranges from 67 to 129 cases per 100,000 children under 5 years of age, and the annual incidence of Haemophilus meningitis is 19 to 69 cases per 100,000 children (Broom C. V., Pediatry Infect Dis 779-782, 1987). Haemophilus influenzae biovargroup aegyptius is mainly responsible for conjunctivitis, and certain strains are responsible for Brazilian purpuric fever (BPF), a serious invasive disease in children under 10 years of age (Brenner et al., J. Clin. Microbiol. 26:1524-1534, 1988).
The quick and accurate diagnosis of H. influenzae is important to treat the various diseases caused by this pathogen. However, most known diagnostic methods are slow or fairly non-specific. Diagnosis of Haemophilus influenzae is traditionally performed by microbacterial methods. Usually, Haemophilus colonies appear after overnight incubation on a selective chocolate 7% horse blood agar plate incubated at 37.degree. C. in moistened air supplemented with 7% carbon dioxide. Haemophilus colonies are then speciated and serotyped by biochemical tests for Gram strain morphology, oxidase reaction, hemolytic activity, porphyrin, and the requirement of growth factors X and V. Because of the time-consuming nature of these techniques, a number of rapid serological methods have recently become available. The vast majority are antibody-based tests, but most lack sufficient specificity for conclusive identification of the presence of Haemophilus influenzae. Therefore, it is the aim of the present invention to provide nucleic acid probes which allow the specific identification of Haemophilus influenzae in a sample in the presence of other bacteria or fungi which are normally present in sampled materials. Such probes may be used in a variety of inexpensive, easy-to-use assay systems which allow an accurate, rapid diagnosis of Haemophilus influenzae related diseases, and which avoid many of the disadvantages associated with traditional microbiological techniques.